What is the term for the formula used to determine the area of a circle?

The area of a circle is determined using the formula that specifically relates to circles. This formula is derived from the mathematical relationship that defines the properties of a circle, particularly in regards to its radius. The correct formulation is expressed as A = πr², where 'A' represents the area, 'π' (pi) is a mathematical constant approximately equal to 3.14, and 'r' is the radius of the circle. This formula allows us to accurately calculate the area enclosed within a circular boundary.

In the context of the choices provided, the term "Circle formula" directly indicates that it pertains to calculations related to circles. The other options—such as the triangle formula, quadratic formula, and Pythagorean theorem—relate to different mathematical concepts entirely. The triangle formula typically pertains to the area of triangles, the quadratic formula is used for solving quadratic equations, and the Pythagorean theorem is relevant to the relationships in right triangles. Thus, identifying the name that corresponds specifically to the area calculation of a circle confirms that the correct answer is indeed the "Circle formula."